Such apparatus are used, for example, in the food industry to supply product slices cut off by a cutting apparatus, such as a high-performance slicer, portion-wise to a downstream processing apparatus, for example to a packaging machine. In particular a belt conveyor or a strap conveyor can be considered as product conveyors. To ensure that only those portions are further processed which satisfy a predefined specification, for example a specific weight or a specific number of slices, incomplete and/or deficient portions are automatically recognized, e.g. with the aid of a sensor, and manually corrected, for example, i.e. are in particular brought up to a demanded desired weight. For this purpose, a corresponding operator, however, requires a certain amount of time so that ultimately the economy of the production plant is restricted by such a correction. Furthermore, on a manual correction, as a consequence of an absence or lack of attention of the operator, it may occur that deficient portions are conveyed on and are finally packaged. Such a further processing of portions of deficient portions is, however, absolutely to be avoided in food production.